From: firstname.lastname@example.org (Robert Dorsett) Date: 25 Mar 93 00:08:38 PST
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The recent FLIGHT INTERNATIONAL report on a 747-100 missed-approach incident mentioned an earlier one, taking place in 1989. I looked it up: the following is some interim coverage of that incident. There don't seem to be overwhelming similarities. -------------------------------- >From FLIGHT INTERNATIONAL, 18-24 July, 1990: BA REPORT REVEALS LHR 747 OVERSHOOT FROM 75ft. "A British Airways Boeing 747, involved in a low offset overshoot incident at Heathrow last November, came as low as 75ft (23m), a confidental letter to BA 747 aircrew from the airline's chief 747 pilot has revealed. The aircraft almost landed outside the airfield boundary (FI, November 29, 1989). "The 747 was inbound from Mauritius via Bahrain. The flight engineer and co-pilot were suffering from gastroenteritis and the copilot had to rest in the cabin for three hours during the flight. "The weather was bad and a Cat 3 landing was needed, the copilot was new and had not completed his initial Cat 3 training detail, so the captain obtained BA permission for the copilot to fly to all-weather minima. "The aircraft, with A autopilot set, intercepted runway 27R ILS. At 13 nm "Land" was selected and the B autopilot engaged. The aircraft captured altitude, then localizer at 10 nm, at which point the engineer called a steady red warning on the B autopilot. The Flight Data Recorder shows that shortly after, both autopilots were disconnected and the aircraft flown manually in the "heading" mode. "Dual Green/Flare Arm annunciators were not obtained from either autopilot. To obtain these, both flight directors (DFs) must annunciate Flare Arm. Each FD can only do this when the aircraft is elow 1500 ft. radio altitude (R), the ILS localizer "on course" conditions have been met for 5 seconds, and "Land" is selected. B autopilot was selected as the centerline was crossed so the conditions were not met. Had the aircraft been flown manually to localizer alignment, then autopilots re-engaged, the aircraft would have captured the ILS and achieved an autoland. "Without the annunciations, autoland was impossible at at 1000' (300m) R the crew should have abandoned the autoland and either gone around or continued to Cat I minima. They continued the approach but did not change their minima. "After deviating to the left, the 747 re-crossed the centreline at 577ft, heading 280 degrees and continued to deviate at an angle of about 5 degrees. At 500' the ILS deviation lights illuminated but the aircraft was allowed to continue to deviate to beyond ILS full-scale deflection and descended to 250' before the autopilots were disconnected. Some 17 seconds elapsed between the ILS deviation lights coming on and autopilot disconnection. "After the autopilots were disconnected the 747 continued to descend for another 7 seconds until power was applied at 120ft and the aircraft began to pitch up very slowly at less than 1 deg/sec (at least 3 deg/sec is normal). The minimum radio altitude recorded was 75 feet. "The captain, who later resigned, subsequently made a successful auto approach and manual landing using B autopilot. In checks the A autopilot was serviceable, the B system roll computer failed."